Methods Of Utilizing Block Copolymer To Form Patterns

ABSTRACT

Some embodiments include methods of forming patterns. A block copolymer film may be formed over a substrate, with the block copolymer having an intrinsic glass transition temperature (T g,0 ) and a degradation temperature (T d ). A temperature window may be defined to correspond to temperatures (T) within the range of T g,0 ≦T≦T d . While the block copolymer is in the upper half of the temperature window, solvent may be dispersed into the block copolymer to a process volume fraction that induces self-assembly of the block copolymer into a pattern. A defect specification may be defined, and the process volume fraction of solvent may be at level that achieves self-assembly within the defect specification. In some embodiments, the solvent may be removed from within the block copolymer while maintaining the defect specification.

TECHNICAL FIELD

Methods of utilizing block copolymer to form patterns.

BACKGROUND

Numerous applications exist in which it is desired to form repeatingpatterns having a small pitch (for example, a pitch of less than about50 nanometers). For instance, integrated circuit fabrication may involveformation of a repeating pattern of memory-storage units (e.g., NANDunit cells, dynamic random access memory [DRAM] unit cells, cross-pointmemory unit cells, etc.).

A variety of methods have been developed for creating patterned maskssuitable for patterning underlying materials during fabrication ofintegrated circuit components. A continuing goal of integrated circuitfabrication is to increase integrated circuit density, and accordinglyto decrease the size of individual integrated circuit components. Thereis thus a continuing goal to form patterned masks having increasingdensities of various patterned features.

A method showing some promise for creating repeating patterns to highdensity involves utilization of block copolymer to form the repeatingpatterns. Unfortunately, there are often numerous defects present in therepeating patterns formed with block copolymers. It would be desirableto develop new methods of forming patterns with block copolymers whichenable repeating patterns to be formed to high density, and with fewerdefects than are presently formed with conventional methods.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic representation of a pattern formed withself-assembly of diblock copolymer.

FIG. 2 is another diagrammatic representation of the pattern shown inFIG. 1.

FIG. 3 is another diagrammatic representation of a portion of thepattern shown in FIG. 1.

FIG. 4 is a diagrammatic representation of a step occurring during theself-assembly of block copolymer.

FIG. 5 is a diagrammatic representation of the utilization of solventduring the self-assembly of block copolymer.

FIG. 6 diagrammatically illustrates thermal treatment of block copolymerto induce self-assembly within the block copolymer.

FIG. 7 diagrammatically illustrates solvent treatment of block copolymerto induce self-assembly within the block copolymer.

FIG. 8 diagrammatically illustrates solvent treatment of block copolymerto induce self-assembly within the block copolymer, and shows a problemthat may occur during some processes.

FIG. 9 diagrammatically illustrates removal of solvent from assembledblock copolymer, and shows a problem that may occur during someprocesses.

FIG. 10 diagrammatically illustrates an example embodiment process forutilizing a combination of thermal processing and solvent treatment toinduce self-assembly within block copolymer.

FIG. 11 diagrammatically illustrates a top view of an exampleconstruction treated in accordance with the embodiment of FIG. 10.

FIG. 12 diagrammatically illustrates an example embodiment process forremoving solvent from an assembled block copolymer.

FIG. 13 diagrammatically illustrates a top view of an exampleconstruction treated in accordance with the embodiment of FIG. 12.

FIG. 14 diagrammatically illustrates another example embodiment processfor removing solvent from an assembled block copolymer.

FIG. 15 diagrammatically illustrates a top view of an exampleconstruction treated in accordance with the embodiment of FIG. 14.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Block copolymers are polymers derived from two or more monomericspecies, and contain two or more homopolymer subunits linked by covalentbonds. The union of the homopolymer subunits may utilize an intermediatelinkage known as a junction block.

Block copolymers may be in the form of diblock copolymers, triblockcopolymers, etc. Example diblock copolymers include polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP); polystyrene-b-poly(ethylene oxide)(PS-b-PEO); polystyrene-b-poly(methylmethacrylate) (PS-b-PMMA); andpolystyrene-b-poly(dimethyl-siloxane) (PS-b-PDMS). The “b” utilized ineach of the above chemical formulas indicates a block linkage. Otherexample block copolymers include materials discussed in U.S. PatentPublication No. 2007/0293041. Diblock copolymers may be genericallyrepresented as A-B, where the “A” represents one of the homopolymersubunits, the “B” represents the other of the homopolymer subunits, andthe hyphen represents a covalent bond or bonds linking to a junctionblock.

A useful property of some block copolymers is that the homopolymersubunits of the copolymers preferentially interact with like subunits,and avoid interactions with dissimilar subunits. For instance, in somediblock copolymers (A-B), the subunits A preferentially interact withother A, the subunits B preferentially interact with other B, and thesubunits A and B preferentially avoid interactions with one another. Thecopolymers may thus self-assemble into repeating patterns. For instance,some copolymers may self-assemble into a repeating pattern that may berepresented as A-B:B-A:A-B:B-A:A-B. In such pattern, the hyphensrepresent covalent bonds and the colons represent non-covalentinteractions.

FIG. 1 shows a construction 10 comprising a substrate 12 having adiblock copolymer pattern extending thereover.

Substrate 12 may comprise, for example, a monocrystalline semiconductorwafer (for example, a monocrystalline silicon wafer), either alone or inassemblies with other materials. The terms “semiconductive substrate”and “semiconductor substrate” mean any constructions comprisingsemiconductive material, including, but not limited to, bulksemiconductive materials such as semiconductive wafers (either alone orin assemblies comprising other materials thereon), and semiconductivematerial layers (either alone or in assemblies comprising othermaterials). The term “substrate” means any supporting structure,including, but not limited to, semiconductive substrates.

The substrate 12 has an upper surface 15 to which subunit A of thediblock copolymer has more affinity than does subunit B of thecopolymer, (for instance, surface 15 may be more wettable by subunit Athan by subunit B). Accordingly, the diblock copolymer orients so thatsubunits A are directed toward surface 15. The first layer of A-Bcopolymer along surface 15 may be referred to as a brush layer 17.Additional levels of A-B copolymer are formed over the brush layer, andself-assembly of the copolymer may be induced by various conditions(with example conditions utilizing one or both of thermal treatment andsolvent treatment, as discussed in more detail below).

The self-assembly has formed a pattern comprising two different domains.One of the domains corresponds to features 14 of A subunits (demarcatedby dashed lines 19 in FIG. 1), and the other of the domains correspondsto a surrounding region 16 of B subunits. The features 14 may becylinders or micelles. For instance, the features may be cylinders thatextend parallel to the surface 15 of substrate 12, and that extend inand out of the page relative to the cross-sectional view of FIG. 1.Alternatively, the features 14 may be micelles, such as sphericalmicelles, arranged in a two-dimensional array across the surface 15 ofsubstrate 12. In some embodiments, the features 14 may be formed inregistration to lithographically-formed structures, and may be used toeffectively multiply the pitch density of such structures.

Although the surrounding region 16 is shown to be the B subunits and thefeatures 14 are shown to be the A subunits, in other embodiments thepattern may be reversed so that the surrounding region 16 contains the Asubunits and the features 14 contain the B subunits.

The pattern of FIG. 1 may be diagrammatically represented with thesimplified drawing shown in FIG. 2. A boundary between the brush layer17 and the B subunit region 16 is represented with a dashed line 21 inFIG. 2. The features 14 form a monolayer over substrate 12.

FIG. 3 shows yet another way to illustrate the pattern of FIG. 1. Only aportion of the construction of FIGS. 1 and 2 is shown in FIG. 3; and thebrush layer 17 (FIGS. 1 and 2) and substrate 12 (FIGS. 1 and 2) are notshown. A few separate diblock molecules 18 are diagrammaticallyillustrated in FIG. 3. Each diblock molecule has an A subunit(represented with a heavier line), a B subunit (represented with alighter line) and a junction block connecting the A and B subunits toone another (the junction blocks are represented with knots 20 betweenthe A and B subunits of individual molecules). The A subunits are showninteracting with one another to assemble into the domains 14, while theB subunits assemble into the domain 16.

FIG. 4 shows an expanded region of the construction of FIG. 3 at anintermediate step during the assembly of domains 14 and 16. A diblockmolecule 18 a is shown migrating through a B subunit domain 16 duringthe self-assembly process (the migration is illustrated with the arrow23). The movement of molecule 18 a through domain 16 requires asubstantial amount of energy because such movement includes moving the Asubunit of molecule 18 a through the B subunit domain 16. TheFlory-Huggins interaction parameter X (Greek letter chi) may be used tocharacterize the difficulty of moving a diblock molecule 18 a during aself-assembly process; with lower values of X indicating highermobilities of diblock molecules through the various domains. Theeffective Flory-Huggins parameter (X_(eff)) may be related totemperature and solvent concentration through the relationship ofEquation 1.

$\begin{matrix}{X_{eff} = {\left( {1 + \frac{b}{T}} \right){\Phi_{p}.}}} & {{Equation}\mspace{14mu} 1}\end{matrix}$

In such relationship, a and b are material specific constants, T is thetemperature (in Kelvins), and Φ_(p) is the volume fraction of polymer(specifically, block copolymer) in a composition containing both solventand polymer. In other words Φ_(p) is related to the volumes of polymer(V_(p)) and solvent (V_(s)) in a block copolymer/solvent compositionthrough the relationship of Equation 2.

$\begin{matrix}{\Phi_{p} = {\frac{V_{p}}{V_{p} + V_{s}}.}} & {{Equation}\mspace{14mu} 2}\end{matrix}$

Equations 1 and 2 indicate that X_(eff) may be decreased by increasing atemperature and/or by providing increasing amounts of solvent into thesystem (the solvent may be a single “neat” chemical composition [forinstance, toluene], or may be a blend of chemical compositions [i.e., aso-called solvent blend]). There will be a range of conditions suitablefor self-assembly of copolymer. Specifically, some temperatures will notbe suitable for self-assembly of copolymer, either because thetemperatures are below a glass transition temperature, T_(g) (which isdiscussed below), or because the temperatures are above a degradationtemperature, T_(d), of the copolymer. Also, some solvent concentrationswill not be suitable to induce self-assembly of the copolymer, eitherbecause the concentrations are too low to meaningfully affect X_(eff),or because the solvent concentrations are so high that the productX_(eff)*N (where N is the average number of monomer units per chain)drops below the threshold for transition from ordered to disorderedstates. This threshold varies depending on the volume fraction of thevarious individual blocks in the total block copolymer; but in theory isalways ≧10.5, and in practice is usually at least 20. For at least theabove-described reasons, a self-assembly process will have a range ofsuitable solvent concentrations, and a range of suitable temperatures.

The solvents utilized to induce self-assembly of block copolymer aregenerally solvents that interact with all of subunits of the blockcopolymer (for instance, solvents which interact with both subunits of adiblock copolymer). The solvents may be neutral-wetting relative to thesubunits of the block copolymer (i.e., may have no preference for anysubunit relative to another) or may exhibit some preference for onesubunit relative to another. The relative preference of solvent for onesubunit of block copolymer relative to other subunits may be estimatedfrom Hildebrand or Hansen solubility parameters.

FIG. 5 shows the construction of FIG. 4 in an embodiment in whichsolvent (diagrammatically illustrated with asterisks (*)) is withindomain 16 to assist molecule 18 b in moving through the domain 16. Insome aspects, the solvent may be thought of as functioning analogouslyto a surfactant, and specifically as providing an interface between theA subunits of some copolymer molecules and the B subunits of othercopolymer molecules to facilitate movement of different types ofsubunits past one another.

An aspect of some embodiments is recognition that it may be advantageousto utilize a combination of temperature and solvent concentration totailor the effective Flory-Huggins interaction parameter, X_(eff), of ablock copolymer system. The tailoring of X_(eff) may be utilized duringthe self-assembly of the block copolymer to achieve an assembledpattern; with such pattern having either no detectable defects, orhaving defects present to at or below a predetermined threshold. Suchthreshold may be established relative to a desired application of thepattern. For instance, if the pattern is to be utilized for fabricationof highly integrated circuitry, the threshold may be set at a levelcomparable to that expected for photolithographic patterning ofphotoresist masks; which may correspond to less than or equal to 0.3defects per square centimeter of surface of the self-assembledcopolymer.

In addition to X, block copolymers may also be characterized in terms ofthe glass transition temperature (T_(g)) of the block copolymers. Theglass transition temperature of a block copolymer is the temperature atwhich the block copolymer melts; or, in other words, the temperature atwhich the block copolymer transforms from a “set” phase into a mobilephase. The set phase has characteristics of a solid (and may be, forexample, a glassy solid), and the mobile phase has characteristics of aliquid (and may be, for example, a viscoelastic liquid). A blockcopolymer composition may have an intrinsic glass transition temperature(T_(g,0)) which is the glass transition temperature of the blockcopolymer in a pure (i.e., neat) state, in the absence of any solvent.

The glass transition temperature of a block copolymer composition may beinfluenced by solvent incorporation into the composition, and thus thecomposition may have a glass transition temperature other than T_(g,0)if the composition has solvent incorporated therein. If a solventinteracts with all of the subunits of a block copolymer, the glasstransition temperature will generally be inversely related to thesolvent concentration in the composition containing the block copolymerand solvent. Thus, increasing the solvent concentration will decreasethe glass transition temperature of the block copolymer/solventcomposition.

In some embodiments, the self-assembly of block copolymer is conductedunder particular process conditions, which include both a processtemperature (T_(P)), and a process solvent volume (V_(s,P)) within theblock copolymer/solvent composition. The block copolymer/solventcomposition can have a glass transition temperature (T_(g,P)) under suchprocess conditions, with T_(g,P) being related to V_(s,P); and withT_(g,P) being less than the intrinsic glass transition temperature(T_(g,0)) of the block copolymer.

Although the glass transition temperature and X_(eff) may be bothinfluenced by solvent concentration, the glass transition temperature isa separate parameter from X_(eff), and generally behaves independentlyof X_(eff).

The process of forming a pattern with copolymer may involve thefollowing steps in some embodiments. First, the copolymer is spreadacross a substrate. Next, the copolymer is subjected to appropriateconditions to induce self-assembly of a pattern within the copolymer;with any defects present in the pattern being present to at or below apredetermined threshold level of the defects. The self-assembledcopolymer is then quenched to lock the pattern into a state that remainsstable as the assembled block copolymer is transitioned to ambientconditions.

As discussed above, some embodiments utilize a combination oftemperature and solvent concentration to tailor X_(eff) during selfassembly of block copolymer. Prior to discussing the embodiments thatutilize the combination of temperature and solvent concentration, it isuseful to discuss example processes that utilize temperature alone, orsolvent alone, during self assembly of block copolymer.

An example process of utilizing temperature treatment alone to form aself-assembled pattern within block copolymer is illustrated in FIG. 6.An initial step (shown at the top of the figure) comprises spreadingblock copolymer 20 over substrate 12. The construction 10 is thensubjected to a thermal treatment (diagrammatically illustrated as theapplication of heat to the construction). The thermal treatment enablesmicro-phase separation and self-assembly of the copolymer to form thepattern comprising the domains 14 within the surrounding domain 16 (thebrush layer is not labeled in FIG. 6, but would also be formed).

After the pattern of domains 14 and 16 is formed, the construction 10 iscooled to below T_(g,0) (diagrammatically illustrated as removal of heatfrom the construction) to lock the pattern into place over the substrate12.

The thermal processing of FIG. 6 will not work for some copolymersystems. For instance, some systems (like PS-b-PDMS) have too high of aX_(eff) value to be processed with a thermal treatment alone, andX_(eff) cannot be brought into a suitable regime for self-assembly ofthe copolymer at temperatures below the degradation temperature, T_(d),of the copolymer. Temperatures above T_(d) are not practical as theywould degrade, or destroy, the copolymer.

An example process of utilizing a solvent treatment alone to form aself-assembled pattern within block copolymer is illustrated in FIG. 7.An initial step (shown at the top of the figure) comprises spreading theblock copolymer 20 over the substrate 12 to form a film of the blockcopolymer across the substrate. The construction 10 is then subjected tosolvent treatment (diagrammatically illustrated as the application ofsolvent vapor). The construction may be provided in a sealed chamber andthe solvent treatment may comprise flowing solvent vapor into thechamber to achieve a desired partial pressure of solvent vapor withinthe atmosphere in the chamber. The amount of solvent incorporated intothe block copolymer (or, in other words, the resulting volume fractionof solvent in the film) may be proportional to the partial pressure ofthe solvent vapor in the chamber atmosphere. The solvent incorporatedinto the copolymer is indicated in the figure with asterisks (*)representing the solvent. The solvent incorporation enables micro-phaseseparation and self-assembly of the copolymer to form the patterncomprising the domains 14 within the surrounding domain 16 (the brushlayer is not labeled in FIG. 7, but would also be formed).

After the pattern of domains 14 and 16 is formed, the solvent is removedfrom within the assembled block copolymer (diagrammatically illustratedas removal of solvent vapor) to lock the pattern into place over thesubstrate 12.

FIG. 7 shows an idealized application in which solvent is utilized toform a desired self-assembled pattern within block copolymer. Inpractice, multiple problems may be confronted when attempting to utilizesolvent and block copolymer to form patterns corresponding to monolayersof self-assembled structures. A couple of such problems are describedwith reference to FIGS. 8 and 9.

FIG. 8 shows a process similar to that discussed above with reference toFIG. 7. However, the incorporation of solvent causes a substantialswelling volume change within the block copolymer, so that the resultingpattern of domains 14 and 16 is stacked into multiple layers, causingelevated regions 22 to be formed within the pattern of domains 14 and16. In the shown application, the pattern of domains 14 and 16 isbifurcated into regions of n and n+1 layers of domains 14. In otherapplications, there may be regions of n+2 layers of domains 14, n+3layers, etc., depending on the amount of a swelling induced by theincorporation of the solvent into the block copolymer. When the solventis subsequently removed, the pattern may remain stacked into themultiple layers (as shown), or may collapse into a defect-riddenmonolayer. Regardless, the pattern remaining after the solvent removalis not the desired single layer shown in FIG. 7.

FIG. 9 shows a problem that may occur as solvent is removed during thelast stage of the FIG. 7 process. Specifically, as the solvent isremoved the copolymer/solvent composition changes to a copolymer-onlycomposition, with a corresponding decrease in volume. Such volumedecrease leads to rupture of the self-assembled block copolymer, whichis illustrated as formation of holes 24 within the pattern of domains 16and 14. In the shown embodiment, the illustrated hole 24 penetrates tothe brush layer (shown as 17 in FIG. 2), but not to the surface ofsubstrate 12. In other embodiments, at least some of the holes maypenetrate through the brush layer and to the upper surface of thesubstrate. FIG. 9 shows a pattern within domains 14 and 16 changing asthe solvent is removed and the copolymer deswells. Specifically, both ofdomains 14 and 16 are expanded in the swollen pattern relative to thesize of such domains in the deswollen pattern. Such effect may occur tosome extent whenever solvent is utilized to induce self-assembly ofblock copolymer, but is not shown in the other drawings of thisapplication in order to simplify the presentation of other concepts thatare intended to be illustrated with such drawings. The magnitude of sizechange induced in domains 14 and 16 in proceeding from a deswollen staterelative to a swollen state, or vice versa, may be reduced by reducingthe volume fraction of solvent utilized to produce the swollen state.

The problems of FIGS. 8 and 9 may be alleviated, or even eliminated, byminimizing the amount of solvent, and subsequent volume change, utilizedto induce self-assembly of block copolymer. Some of the embodimentsdescribed herein utilize a combination of thermal treatment and solventtreatment to induce self-assembly of block copolymer, with the thermaltreatment being conducted at very high temperatures (i.e., temperaturesclose to the degradation temperature, T_(d)) so that the amount ofsolvent utilized for the solvent treatment may be kept at minimallevels. Also, the problem of FIG. 9 may be alleviated, or eveneliminated, by using a small amount of solvent in combination withutilizing rapid quenching of a self-assembled pattern of block copolymerto lock the pattern into place. Some of the embodiments described hereinutilize one or both of rapid cooling and rapid solvent removal for therapid quenching utilized to lock the self-assembled pattern of blockcopolymer into place.

FIGS. 10-15 illustrate some example embodiments in which combinations ofsolvent treatment and thermal treatment are utilized duringself-assembly of block copolymer, and/or in which rapid quenching isutilized to lock self-assembled block copolymer into the self-assembledconfiguration.

Referring to FIG. 10, a construction 10 comprises a film of blockcopolymer 20 formed over a substrate 12. The block copolymer has anintrinsic glass transition temperature (T_(g,0)) and a degradationtemperature (T_(d)). A temperature window is defined to be a range oftemperature that is greater than or equal to T_(g,0) and less thanT_(d). In other words, the temperature window comprises a range oftemperatures (T) corresponding to T_(g,0)≦T<T_(d).

The block copolymer is exposed to thermal energy (represented in FIG. 10as exposing the construction 10 to heat) to raise a temperature of theblock copolymer. In some embodiments, it is desired to optimize theeffective Flory-Huggins interaction parameter X_(eff) duringself-assembly of block copolymer so that the parameter is low enough toallow diffusion of the block copolymer molecules through the variousdomains established during self-assembly, and yet high enough so that anequilibrium defect concentration is within a predetermined tolerance.For instance, the tolerance for the defect concentration may be set to alimit suitable for highly integrated circuitry (which may be less thanor equal to 0.3 defects per square centimeter of surface area, and insome applications may be less than or equal to 0.03 defects per squarecentimeter of surface area).

As discussed above, X_(eff) may be decreased by increasing thetemperature of a block copolymer composition and/or by increasing asolvent concentration within the block copolymer. However, the increasein the solvent concentration will lead to swelling and a correspondingchange in volume in the block copolymer/solvent composition. Largevolume changes can problematically induce defects of the type describedwith reference to FIGS. 8 and 9. Some embodiments include utilization ofboth temperature and solvent to induce self assembly of block copolymerto enable X_(eff) to be tailored for the block copolymer systems, anduse relatively high temperatures during the self-assembly to therebyreduce the amount of solvent utilized to achieve desired values ofX_(eff). In such embodiments, a process temperature utilized duringself-assembly of block copolymer may be in the upper portion of therange corresponding to T_(g,0)≦T<T_(d). For instance, in someembodiments the process temperature may be in the upper half of suchrange, upper third of such range, upper quarter of such range, or uppertenth of such range.

While construction 10 is held at the process temperature, the blockcopolymer is exposed to solvent vapor to thereby introduce solvent intocopolymer 20 (the solvent is diagrammatically illustrated as asterisks(*) in FIG. 10). The construction 10 may be retained within a chamber asit is held at the process temperature and exposed to the solvent vapor.The volume fraction of solvent (V_(s) of equation 2) incorporated intocopolymer 20 may be proportional to the partial pressure of solventvapor within the chamber environment. In some embodiments, a minimalamount of solvent vapor is provided to initiate self-assembly within theblock copolymer. The utilization of the minimal amount of solvent vapormay enable problems of the type described above with reference to FIGS.8 and 9 to be avoided, and thus may enable the block copolymer to selfassemble into a pattern of two or more domains (such as the illustratedpattern of domains 14 and 16 shown in FIG. 10) that has very fewdefects.

In some embodiments, X_(eff) is tailored by using the combination of ahigh process temperature (T_(P)), and a low process solvent volume(V_(s,P)) during the self-assembly process. In specific embodiments,X_(eff) may be tailored to achieve a number of defects corresponding toless than or equal to 0.3 defects per square centimeter of surface ofthe self-assembled block copolymer, or even less than or equal to 0.03defects per square centimeter of surface of the self-assembled blockcopolymer. The processing of FIG. 10 can thus be utilized to achievedefect specifications of less than or equal to 0.3 defects per squarecentimeter, or even less than or equal to 0.03 defects per squarecentimeter.

Another way to quantitate the number of defects, rather than as aquantity per unit area, is to directly quantitate the number ofdefective units relative to the number of non-defective units. In someembodiments, X_(eff) may be tailored through high temperature and lowsolvent concentration to achieve no more than one defective unit per onebillion units of assembled block copolymer; with the term “unit”referring to a distinct domain region, such as the individual domainregions 14 of FIG. 10.

FIG. 11 shows a top view of the construction of FIG. 10, anddiagrammatically illustrates defective units 30 present across anexpanse of the self-assembled block copolymer. Such defective units maycorrespond to, for example, stacking regions of the type shown in FIG.8, voids as shown in FIG. 9, or point defect patterns—such asdislocations. Conventional methods for self-assembly of block copolymermay lead to a relatively high number of defects across the expanse ofself-assembled block copolymer. In contrast, embodiments describedherein that induce self-assembly under conditions having relatively hightemperatures in combination with low concentrations of solvent mayeliminate defective units, or may at least reduce the number ofdefective units to within a tolerance suitable for fabrication of highlyintegrated circuitry.

The block copolymer and solvent utilized in the embodiment of FIG. 10may be any suitable block copolymer and solvent. However, the embodimentof FIG. 10 may be particularly suitable for utilization with blockcopolymers that cannot be self-assembled utilizing thermal processingalone (e.g., block copolymers that have X_(eff) values that are notreduced into a suitable regime for self-assembly at temperature valuesbelow the T_(d) of the block copolymers). Among the blockcopolymer/solvent combinations that may be particularly suited for theembodiment of FIG. 10 is the combination of the block copolymerPS-b-PDMS and the solvent toluene.

The cross-sectional view of FIG. 10 shows the domains 14 as circleswithin the domain 16. In some embodiments the domains 14 may becylinders that extend parallel to an upper surface of substrate 12, andthat extend in and out of the page relative to the cross-sectional viewof FIG. 10 to form a monolayer pattern across substrate 12 (with themonolayer pattern being a single layer of domains 14 across thesubstrate as opposed to the problematic n+1 layer patterns describedabove with reference to FIG. 8). In other embodiments, the domains 14may be spherical micelles. If the domains 14 are spherical micelles,they may be in a two-dimensional arrangement across the upper surface ofsubstrate 12, with such arrangement corresponding to, for example,hexagonal closest packed unit cells or cubic unit cells forming amonolayer pattern across substrate 12.

After the self-assembly of the block copolymer of FIG. 10, the solventmay be removed to leave the patterned domains of the assembled blockcopolymer. One of the problems with prior art methods of solvent removalis that film rupturing, or other defects, may occur during thedeswelling that accompanies removal of the solvent from the film. Forinstance, FIG. 9 describes a problem of hole formation accompanyingsolvent removal.

In some embodiments, the removal of solvent from assembled blockcopolymer is accomplished under conditions which alleviate, or may eveneliminate, defect formation during the solvent removal. Such conditionsmay include removal of the solvent after very rapidly reducing atemperature of the self-assembled block copolymer to a temperature lessthan T_(g,P) of the block copolymer, and/or very rapid removal of thesolvent from the self-assembled block copolymer. It can be preferredthat the removal of the solvent be accomplished while maintaining adesired defect specification within the assembled block copolymer. Thus,in some embodiments the solvent is removed while maintaining a defectspecification of less than or equal to 0.3 defects per square centimeterof the assembled block copolymer, or even of less than or equal to 0.03defects per square centimeter of the assembled block copolymer.

FIG. 12 illustrates example processing for removal of solvent fromself-assembled block copolymer by utilizing a temperature change priorto the solvent removal. The top construction of FIG. 12 may correspondto the construction formed by the processing of FIG. 10. At an initialstep of FIG. 12 the construction 10 is cooled (diagrammaticallyillustrated by heat removal from the construction). The cooling maycomprise very rapid cooling of the block copolymer to a temperaturebelow T_(g,P) to lock the copolymer into the self-assembledconfiguration. The rapid cooling may be accomplished by retainingconstruction 10 on a thermally-controlled chuck, and then rapidlyreducing a temperature of the chuck to thereby rapidly reduce thetemperature of the block copolymer. In other embodiments, the rapidcooling may comprise transferring the construction 10 onto a surfacethat has been pre-equilibrated to a temperature below T_(g,P).Alternatively, or additionally, the block copolymer may be cooled byproviding the construction 10 within a chamber, and flowing cold gas(i.e., gas at a temperature below T_(g,P)) through such chamber torapidly cool the block copolymer. The rate of cooling of the blockcopolymer with the gas may depend on the temperature of the gas (withlower temperatures leading to faster cooling) and the flow rate of thegas (with faster flow rates leading to faster cooling). In someembodiments, the gas may be flowed at a rate of at least about 1 chambervolume per second, and/or may be provided at a temperature that is atleast about 50° C. below T_(g,P).

In some embodiments, the rapid cooling of the block copolymer maycomprise cooling the block copolymer at a rate of at least about 10°C./second, at least about 60° C./second, or even at least about 100°C./second. In some embodiments, the rate of cooling is within a range offrom about 10° C./second to about 60° C./second. The rapid cooling ofthe block copolymer may be referred to as thermal quenching of the blockcopolymer in some embodiments. The term “thermal quenching” refers tothe quenching of rearrangement of the pattern of the block copolymer bycooling the block copolymer to a temperature below T_(g,P).

After construction 10 is cooled, and while keeping the assembled blockcopolymer at a temperature below T_(g,P), the solvent is removed fromthe block copolymer (diagrammatically illustrated in FIG. 12 as removalof solvent vapor). The solvent may be removed with any suitable method.For instance, the solvent may be removed by subjecting construction 10to vacuum. Alternatively, the solvent may be removed by flushingnon-solvent-containing purge gas across construction 10. In someembodiments, the solvent may be removed by flushingnon-solvent-containing purge gas across construction 10 while exposingthe construction to a partial vacuum.

FIG. 13 shows a top view of the construction 10 after the processing ofFIG. 12, and diagrammatically illustrates defective units 40 presentacross an expanse of the self-assembled block copolymer. Conventionalmethods for removing solvent from assembled block copolymer may lead toa relatively high number of defects across the expanse of self-assembledblock copolymer. In contrast, the embodiments described herein thatremove solvent after first rapidly reducing the temperature to belowT_(g,P) may eliminate defective units, or may at least reduce the numberof defective units to within a tolerance suitable for fabrication ofhighly integrated circuitry.

Once the solvent is removed, the self-assembled pattern within the blockcopolymer is stable at temperatures below T_(g,0). The patterned domainswithin the self-assembled block copolymer may be subsequently utilizedto impart a pattern into the underlying substrate 12. For instance, oneof the patterned domains may be selectively removed, or otherwisealtered, relative to the other to form a patterned mask over substrate12. Such patterned mask may be utilized during a subsequent etch topattern structures formed in substrate 12, and/or during a subsequentdopant implant to pattern dopant regions formed in substrate 12.

FIG. 12 illustrates an embodiment in which block copolymer is rapidlycooled prior to solvent removal in order to lock the block copolymerinto a self-assembled pattern. In other embodiments, the solvent may berapidly removed in order to lock the block copolymer into theself-assembled pattern. The removal of the solvent raises the glasstransition temperature T_(g) of the copolymer composition from T_(g,P)to T_(g,0). Since the self-assembly process is at the processtemperature T_(p), the removal of the solvent raises the glasstransition temperature to value higher than the temperature of the blockcopolymer, and thereby ceases further changes within the self-assembledblock copolymer. The rapid solvent removal may be conducted withoutfirst reducing a temperature of the block copolymer to less than T_(P)in some embodiments, and in other embodiments may be conducted afterfirst reducing a temperature of the block copolymer to less than T_(P).

FIG. 14 illustrates construction 10 at a processing stage subsequent tothat of FIG. 10, and shows solvent being rapidly removed from theconstruction (diagrammatically illustrated as rapid removal of solventvapor). The rapid removal of the solvent may be accomplished by rapidlyflowing multiple chamber volumes of non-solvent-containing purge gasthrough a chamber containing construction 10 therein. For instance, insome embodiments at least 10 chamber volumes of non-solvent-containingpurge gas may be flowed through the chamber at a rate of at least about1 chamber volume per second. The purge gas may comprise any suitablecomposition or combination of compositions, and in some embodiments maycomprise, consist essentially of, or consist of one or more of argon,carbon dioxide and nitrogen. In some embodiments, the rate of flow ofthe purge gas through the chamber may be faster than 1 chamber volumeper second, and may be, for example, at least about 10 chamber volumesper second.

The purge gas utilized to remove solvent may be at any suitabletemperature. In some embodiments, the removal of the solvent increasesthe block copolymer glass transition temperature T_(g) to a value muchhigher than T_(g,P). In such embodiments, the purge gas may be heatedrelative to the process temperature utilized during the self-assembly ofthe block copolymer without inducing detrimental glass flow within theblock copolymer. The heating of the purge gas may enhance the rate ofremoval of solvent. Alternatively, the purge gas may be cooled relativeto the process temperature utilized during the self-assembly of theblock copolymer in order to ensure that the temperature of the blockcopolymer remains below the glass transition temperature of the blockcopolymer during the removal of the solvent.

The solvent removal may include utilization of partial vacuum inaddition to the sweep of purge gas through the chamber in someembodiments; and in other embodiments the solvent removal may compriseutilization of vacuum without utilization of purge gas.

FIG. 15 shows a top view of the construction after the processing ofFIG. 14, and diagrammatically illustrates defective units 50 presentacross an expanse of the self-assembled block copolymer. Conventionalmethods for removing solvent from assembled block copolymer may lead toa relatively high number of defects across the expanse of self-assembledblock copolymer. In contrast, embodiments described herein that removerapidly remove solvent may eliminate defective units, or may at leastreduce the number of defective units to within a tolerance suitable forfabrication of highly integrated circuitry.

As discussed above, the patterned block polymers formed by the variousembodiments described herein may be utilized to pattern underlyingsemiconductor substrates. In some embodiments such semiconductorsubstrates may be then incorporated into electronic systems. Theelectronic systems may be any suitable systems, including systems of thebroad range that includes clocks, televisions, cell phones, personalcomputers, automobiles, industrial control systems, and aircraft.

In compliance with the statute, the subject matter disclosed herein hasbeen described in language more or less specific as to structural andmethodical features. It is to be understood, however, that the claimsare not limited to the specific features shown and described, since themeans herein disclosed comprise example embodiments. The claims are thusto be afforded full scope as literally worded, and to be appropriatelyinterpreted in accordance with the doctrine of equivalents.

1. A method of forming a pattern, comprising: forming block copolymerover a substrate; the block copolymer having an intrinsic glasstransition temperature (T_(g,0)) and having a degradation temperature(T_(d)); a temperature window being defined as a range of temperaturethat is greater than or equal to T_(g,0) and less than T_(d); and whilethe block copolymer is within the upper half of the temperature window,providing solvent into the block copolymer to a volume fraction thatwill induce self-assembly of the block copolymer into a patterncomprising two or more domains; the self-assembled block copolymerhaving less than a predetermined number of defects.
 2. The method ofclaim 1 wherein the solvent is a single chemical composition.
 3. Themethod of claim 1 wherein the solvent is a blend of two or more chemicalcompositions.
 4. The method of claim 1 wherein the solvent volumefraction induces no more than 0.3 defects per square centimeter ofsurface of the self-assembled block copolymer.
 5. The method of claim 1wherein the solvent volume fraction induces no more than 0.03 defectsper square centimeter of surface of the self-assembled block copolymer.6. The method of claim 1 wherein the block copolymer is PS-b-PDMS andthe solvent is toluene.
 7. The method of claim 1 further comprising,after inducing the self-assembly, removing the solvent from within theblock copolymer.
 8. The method of claim 1 further comprising, afterinducing the self-assembly, removing the solvent from within the blockcopolymer under conditions which leave the block copolymer in aself-assembled pattern having no more than the predetermined number ofdefects per unit area.
 9. The method of claim 1 further comprising,after inducing the self-assembly, removing the solvent from within theblock copolymer under conditions which leave the block copolymer in aself-assembled pattern having no more than 1 defect per one billionunits.
 10. The method of claim 9 wherein the block copolymer has aprocess glass transition temperature T_(g,P) at the solvent volumefraction utilized during the inducement of the self-assembly, andwherein the conditions used during the solvent removal include coolingthe assembled block copolymer at a rate of at least about 10° C./secondto a temperature below T_(g,P) and then removing the solvent from theblock copolymer while the temperature of the block copolymer remainsbelow T_(g,P).
 11. The method of claim 9 wherein the conditions includeremoving the solvent from the block copolymer by sweeping at least 10chamber volumes of non-solvent-containing purge gas through the chamberat a rate of at least about 1 volume per second.
 12. A method of forminga pattern, comprising: forming a block copolymer film over a substrate;the block copolymer having an intrinsic glass transition temperature(T_(g,0)) and having a degradation temperature (T_(d)); a temperaturewindow being defined to correspond to temperatures (T) within a range ofT_(g,0)≦T<T_(d); while the block copolymer is in the upper half of thetemperature window, providing solvent into the block copolymer to aprocess volume fraction that will induce self-assembly of the blockcopolymer into a pattern comprising two or more domains; a defectspecification being defined to be less than or equal to 0.3 defects persquare centimeter of surface of the self-assembled block copolymer; theprocess volume fraction being at a level that achieves self-assemblywithin the defect specification; and after inducing the self-assembly,removing the solvent while maintaining the defect specification.
 13. Themethod of claim 12 wherein the self-assembly forms a monolayer ofcylinders that extend parallel to an upper surface of the substrate. 14.The method of claim 12 wherein the self-assembly forms a monolayer of atwo-dimensional array of spherical micelles across an upper surface ofthe substrate.
 15. The method of claim 12 wherein the defectspecification is less than or equal to 0.03 defects per squarecentimeter of surface of the self-assembled block copolymer.
 16. Themethod of claim 12 wherein the block copolymer has a process glasstransition temperature T_(g,P) at the process volume fraction of solventutilized during the inducement of the self-assembly, and wherein thesolvent is removed under conditions which include cooling the assembledblock copolymer at a rate of at least about 10° C./second to atemperature below T_(g,P) and then removing the solvent from the blockcopolymer while the temperature of the block copolymer remains belowT_(g,P).
 17. The method of claim 12 wherein the solvent is removed underconditions which include sweeping at least 10 chamber volumes ofnon-solvent-containing purge gas through the chamber at a rate of atleast about 1 volume per second.
 18. A method of forming a pattern,comprising: forming a block copolymer film over a substrate; providingsolvent into the block copolymer to a volume fraction that will induceself-assembly of the block copolymer into a pattern comprising two ormore domains; the block copolymer having a process glass transitiontemperature T_(g,P) at the volume fraction of solvent utilized duringthe inducement of the self-assembly; after inducing the self-assembly,thermally quenching the self-assembled block copolymer to a temperaturebelow T_(g,P); the thermal quenching comprising a reduction intemperature of the block copolymer at a rate of at least about 10°C./second; and after the thermal quenching, removing the solvent. 19.The method of claim 18 wherein the rate is at least about 60° C./second.20. The method of claim 18 wherein the rate is at least about 100°C./second.
 21. The method of claim 18 wherein the thermal quenching isconducted while the block copolymer and substrate are within a chamber,and wherein the thermal quenching comprises flowing gas through thechamber, the gas being at a temperature below said T_(g,P) as the gas isflowed into the chamber.
 22. The method of claim 18 wherein the thermalquenching is conducted while the block copolymer and substrate arewithin a chamber, wherein the substrate is supported by atemperature-controlled chuck, and wherein the thermal quenchingcomprises cooling the chuck to a temperature below T_(g,P).
 23. Themethod of claim 18 wherein the thermal quenching comprises transferringthe block copolymer and substrate onto a surface that is at atemperature below T_(g,P).
 24. The method of claim 18 wherein thethermal quenching is conducted while the block copolymer and substrateare within a chamber, and further comprising drawing vacuum within thechamber during the removal of the solvent.
 25. The method of claim 18wherein the thermal quenching is conducted while the block copolymer andsubstrate are within a chamber, and further comprising flowingnon-solvent-containing purge gas through the chamber during the removalof the solvent.
 26. The method of claim 18 wherein the thermal quenchingis conducted while the block copolymer and substrate are within achamber, and further comprising flowing non-solvent-containing purge gasthrough the chamber at a rate of at least about 1 chamber volume persecond of the purge gas during the removal of the solvent.
 27. A methodof forming a pattern, comprising: forming a block copolymer film over asubstrate; while the block copolymer and underlying substrate are in achamber, providing solvent into the block copolymer to a volume fractionthat will induce self-assembly of the block copolymer into a patterncomprising two or more domains; and after inducing the self-assembly,removing the solvent from the block copolymer by sweeping at least 10chamber volumes of non-solvent-containing purge gas through the chamberat a rate of at least about 1 volume per second.
 28. The method of claim27 wherein the purge gas is heated relative to a temperature utilized toinduce the self-assembly.
 29. The method of claim 27 wherein the purgegas is cooled relative to a temperature utilized to induce theself-assembly.
 30. The method of claim 27 wherein the purge gas iscooled to below a glass transition temperature of the copolymer at thevolume fraction of solvent utilized to induce the self-assembly.
 31. Themethod of claim 27 wherein a partial vacuum is applied during the sweepof the purge gas through the chamber.
 32. A method of forming a pattern,comprising: forming a block copolymer film over a substrate; while theblock copolymer and underlying substrate are in a chamber, providingsolvent into the block copolymer to a volume fraction that will induceself-assembly of the block copolymer into a pattern comprising two ormore domains; and after inducing the self-assembly, removing the solventfrom the block copolymer with vacuum.
 33. The method of claim 32 whereinthe block copolymer has an intrinsic glass transition temperature(T_(g,0)) and has a degradation temperature (T_(d)); wherein atemperature window is defined to correspond to temperatures (T) withinthe range of T_(g,0)≦T<T_(d); and wherein the block copolymer is in theupper half of said temperature window during the inducement of theself-assembly.
 34. The method of claim 32 wherein, during the removal ofthe solvent, the block copolymer is at a temperature below a glasstransition temperature of the copolymer at the volume fraction ofsolvent utilized to induce the self-assembly.
 35. The method of claim 34wherein the self-assembled pattern is a repeating pattern, and whereinthere is no more than 1 defect per one billion units in the repeatingpattern after the removal of the solvent.